Countersinking tool



p 1949- R. E. BAYLESS 2,482,535

COUNTER-SINKINQ TOOL Filed May 4, 1946 INVENTO ausaupaam a J ms ATTORNEYS the work by one cutting cutting edge will not such ridge -cause the entire tool to jump or chatter. .said next succeeding cutting edge will move Patented Sept. 20. 1949 ES PATENT OFFICE COUNTERSINKING" TOOL Russell E. Bayless, Dayton, Ohio, assignor to General Motors Corporation, Detroit,' Mich, a corporation of Delaware Application May 4, 1946, serial No. 667,396

- This invention relates 'to a counter-sinking tool to be'used for cutting a chamfered or other enlargement in the upper part of ahole, usually for the reception of the head of a bolt, screw or rivet wholly or partly below the surface.

Various forms of counter-sinking tools are now well known, but certain difficulties are experienced in their use. Many such prior tools are subject to vibration and chattering and have to be run at quite low speeds in order to avoid excessive chattering and jumping around of the tool relative to the center line of the hole being countersunk.

. An object of this inve'ntion is to provide a pilot- .less counter-sinking tool which may be run at frelative high speeds without chattering or tending .to jump off "center and which will make a smooth even out without throwing up rough edges or burrs at either the inner or outer diameter of the out. I 'An object is to provide a counter sinking tool .having a series of cutting edges eachof which extends at an angle to the radial direction when looking axially at the end of the tool.- Due to this feature all parts of the length of 'said'cutting edges move at a substantial angle to the direction of said edges rather than in a direction'perpendicular thereto and thereby greatly facilitates the cutting operation.

Another object is to provide such a countersinking tool having a series of cutting edges some of which extend at one angle to the radial direction while the alternate cutting edges extend at a difierent angle to the radial direction, when looking axially at the end of the tool. Due to this feature each cutting edge cuts thru the work at a slight angle to the cut made by the immediately preceding cutting edge, hence if any slight ridge or depression of any sort happens to be made in edge the next succeeding match up in direction with or depression and thereby tend to But against such ridge or depression at a slight angle thereto and hence provide a smooth non-chattering cut.

Further objects and invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of advantages of the present 7 5Claims. (01. was.)

,off at to the center Fig. 3 is a greatly enlarged view of Fig. 2 showing how the alternate cutting edges extend in different directions relative to the radial direction when-looking axially at the end of the tool.

Fig. 4 is'a section on line 4-4 of Fig. 3 and shows the sectional shape of the three main cutting edges of the tool.

Fig.5 is a section on line 5-5 of Fig. 3 and shows the sectional shape of the three secondary cutting edges of the tool.

Similar reference characters refer to similar parts throughout the several views.

The tool of this invention may be made from fluted core drills of the desired diameter, or this tool may be made from solid round tool steel stock and the main and secondary teeth out therein as described hereinbelow.

In'making the counter-sinking tool shown in thedrawings, the metal of the core drill stock It) having a diameter D is first circular ground to a right cone having the desired angle, shown in Fig. 1 as 82. Next the end of the tool is ground line to provide a flat end surface I I having a diametral dimension approximately one-fourth that of the core drill stock.

tool axially. (as viewed in Fig. 3), said main cutting edges 20 will extend along lines tangent to a circle M whose diameter is approximately onefourth of the outer diameter D of the tool. That is, the'main cutting edges 20 do not extend in a radial direction but extend at the substantial angle A to a radial line drawn thru the axis of thetool (as projected in Fig. 3)

Then the secondary cutting edges 30, which terminate at points 3| in end surface H, are ground in the original lands l3 by grinding open recesses 32 in the conical end surfaces of said lands 13. .According to this invention these secondary cutting edges 30 are so cut that they will extend at a substantially different angle from the main cutting edges 20 relative to the radius -(as projected in Fig. 3).

In Fig. 3, these secondary edges 30 extend on lines tangent to a circle S whose diameter is approximately one-eighth of the outer diameter D of the tool. That is, the

secondary edges 30 extend at an angle B" to a radial line drawn thru the axis of the tool (as 01." jump siig scribed above. The sizes of angles A and B depend upon the radii of circles M and S, respectively. In Fig. 3, since the radius of circle S is one-half that of circle M, angle B will be practically one-half of angle A.

The above-mentioned open recesses 32 are cut in the conical end surfaces of lands l3 to form the secondary teeth 35. These open recesses 32 are cut to a sufficient. depth below the cutting edges 30 to provide suitable open space for the metal chips removed in use by said cutting edges 30. The trailing top surfaces of the secondary teeth 35 are ground back from their cutting edges 30 at an angle of about 7 as shown in Fig. 5. Likewise the trailing top surfaces of themain teeth 25 are ground back from their cutting edges at an angle of about 7 for a. suitable Width, as shown by lines 2:: in Fig. 3 and by point 26 in Fig. 4.

The open recesses 32.. are cut out at a somewhat steeper angle than '7; degrees immediately .trail-ing the lines 25. in order to providethe dc.- sired height to the secondary teeth 35.

Preferably the leading faces of the secondary teeth 35ers. slightly undercut below the cutting edge 30., as shown. inl ig. 5, but this is optional. Since the leading faces of main teeth are formed for 'the most part the adjacent spiral surfaces of rooves i2 (except at their mner ends near points 2 i) these leading faces will; be undercut, as shown After the teeth. 25 311-(135- are cut as: described above,v as. a final operation the end of the tool .is again. circular ground to a true right cone of the desired angle so. as to. bring allthe cutting. 5

ag-afm-st themetal to. hezcut away the main cutting edges 2% and the secondary cutting edges.

follow each. other alternately. If at any time one, of these cuttingedges 26 should leave any sort of slight ridge; or valley. in the metal-being cut: away; the next succeeding cutting edge. will strike such slight: ridge or valley at a different angle, that. is, said succeeding cutting edge will not match up direction with such ridge or valley but will engage same progressively from end; to. e 1 thereof. This will avoid sudden succe cause the tool to vibrate. or chatter;

in p or countersinlring tools all the cutting edges; oveagainst the; metal being cut away at the same- Now if such a.- toolshould vibrate or decrease in the load applied to said in the Work or for any other reason, each of the would leave a slight ridge in the rcafter the cutting edges would e of these ride'esat the same time.

or" such"synchronization and becut edge will match up in direction with ridges. The tool of this invention overcomes such tendency to jump and chatter due to the following several features thereof.

alternate, cutting, edges strike the to be cut away at. dilferent angles. due to .erence between angle. Stand. angle. 13. as

cutting edge which would tend toy due to encounter ng a hard spot :e the tool; to continue to lump or Second, the six cutting edges are not evenly spaced peripherally around the tool, hence there will be no synchronization of all the cutting edges striking previously formed ridges in the work at the same time.

Third, both the main cutting edges 20 and the secondary cutting edges 30 extend inwardly, at a substantial angle ahead of a radial line as viewed in Fig. 3. This means that all of said cutting edges move against the Work at a sub stantial angle to said edges rather than in a direction perpendicular to said edges. This results in a slicing action by all the cutting edges, which of course facilitates the cutting and aids especially in preventing the throwing up of rough edges or burrs at either the inner or outer diameter of the cut.

The above features coacting together cause this counter-sinking tool to cut smoothly at a. much higher operating speed without chattering or tending to vibrate out of alignment as prior countersinking tools do when run at such speeds. Also. thistool eliminates the necessity of. a subsequent burring operation on the cuts made thereby. This tool will. cut smoothly even when used tocountersink a. hole so closely adjacent a second hole or opening, in the work that the. out made; by the tool extends into said second hole or opening.

The tool described in detail hereinahove is made. from a three-fluted core drill and the finished tool has six cutting teeth. It is to-he understood that the principles of this invention canalso. be applied in making a finished tool having more or less than six cutting teeth.

Tools of larger diameters have suflicient conical areas for conveniently making a larger number of teeth. thereon according; to this invention than do tools of smaller diameters.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it. is, to be understood that other forms might adapted, all coming within the scope of the. claims. which follow. 1

What is claimed is as follows:

1-. A rotary counter-sinking too-l: having a. series of main cutting edges and a series. of secondary cutting edges all lying in a geometrical cone, each of said main. cutting: edges lying at a predetermine-d: angle to the: right line of generation of said cone. each of said secondarycutting edges lying. at a, predetermined: angle. to the right: line oi generation of said. cone,. said predetermined angle of. said: main edges being substantially greater than said predetermined: angle of said secondaryedges, all of saidcutting: edges having their inner ends: inclined forwardly relative to tial angle to the rightline of generation of said cone; all; of said cutting edges having their inner ends inclined forwardly relative to the direction of rotation'of said tool.

3., A rotary counter-sinking tool having; a. series of main cutting edges. and. a. series. of secondary cutting edges all lying in; a geometrical cone generated by the rotation of a right line about the tool axis, each of said main cutting edges lying at a predetermined angle to said right line, each of said secondary cutting edges lying at a substantially smaller predetermined angle to said right line, said main'cutting edges being alternately arranged around the cone with said secondary cutting edges. 7 r

4. A rotary counter-sinking tool having a series of main cutting edges and a series of secondary cutting edges all lying in a, geometrical cone generated by the rotation of a right line about the tool axis, each of said main cutting edges lying at a predetermined angle to said right line, each of said secondary cutting edges lying at a substantially different predetermined angle to said rightline, all of said cutting edges having their inner ends inclined forwardly relative to the direction of rotation of said tool.

5. A rotary counter-sinking tool having a series of main cutting edges and a series of sec- 10 tation of said tool.

ondary cutting edges all lying in a geometrical cone generated by the rotation of a right line about the tool axis, each of said main cutting edges lying at a predetermined angle to said right 5 line, each of said secondary cutting edges lying at an angle to said right line which is approximately half that of said main cutting edges, all of said cutting edges having their inner ends inclined forwardly'relative to the direction of ro- R. E. BAYLEss.

15 file of this patent:

UNITED STATES PATENTS Number Name Date 7 1,467,491 Oliver Sept. 11, 1923 Manewich June 4, 1946 

